Rahmawati Minhajat*
Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
*Correspondence: ARahmawati Minhajat, DDepartment of Pathology and Cell Biology, Columbia University, New York, NY, USA. E-mail: rahmawatiminhajatl@columbia.edu
Received: 06 March, 2026; Accepted: 31 March, 2026; Published: 08 April, 2026.
Citation: Rahmawati Minhajat.“Human Leukocyte Antigen-G as a Novel Target for Switch-Based Chimeric Antigen Receptor Natural Killer Cell Therapy of Solid Cancer.”Arch Oncol Res (2026):102.DOI:10.59462/3068- 5273.1.1.102
Copyright: © 2026 Rahmawati Minhajat. This is an open-ac cess article distributed under the terms of the Cre ative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Chimeric antigen receptor (CAR) adoptive cell therapy has demonstrated remarkable clinical success in hematological malignancies; however, its application to solid tumors remains limited [1,2]. Major challenges include the absence of a universally expressed tumor-associated antigen across multiple tumor types, tumor antigen heterogeneity, and the highly immunosuppressive tumor microenvironment (TME) [3,4]. Human leukocyte antigen-G (HLA-G), a non-classical major histocompatibility complex class I molecule with potent immunosuppressive properties, is aberrantly expressed in a wide range of solid malignancies and contributes to immune evasion [5,6]. Here, we propose the development of a switch-based anti-HLA-G chimeric antigen receptor natural killer (CAR-NK) cell platform targeting HLA-G1–G7 isoforms. The construct incorporates an inducible caspase-9 (iCasp9) suicide gene to enhance safety and controllability [7]. This strategy aims to overcome antigen heterogeneity and mitigate on-target/off-tumor toxicity while counteracting tumor-mediated immune suppression [8].
CAR-T cell therapy targeting CD19 has revolutionized the treatment of B-cell malignancies, producing durable responses in refractory leukemia and lymphoma [1]. However, clinical trials in solid tumors have shown limited efficacy due to physical barriers, antigen heterogeneity, and immunosuppressive signals within the tumor microenvironment [2,3].
One major limitation is the lack of a tumor-restricted antigen broadly expressed across solid cancers [4]. Targeting lineage antigens often results in damage to normal tissues expressing the same antigen, leading to on-target/off-tumor toxicity [5]. Furthermore, tumor cells can escape immune pressure by downregulating or mutating target antigens [6].
Natural killer (NK) cells represent an attractive alternative platform for CAR engineering. NK cells exhibit intrinsic cytotoxicity independent of antigen priming and show lower incidence of cytokine release syndrome compared to CAR-T cells [9]. Early-phase clinical studies of CAR-NK therapy have demonstrated promising safety profiles and antitumor activity [10].
HLA-G is a non-classical MHC class I molecule physiologically expressed at immune-privileged sites such as the maternal–fetal interface [11]. In cancer, aberrant HLA-G expression has been reported in breast, ovarian, colorectal, lung, melanoma, glioma, and pancreatic cancers [12]. Elevated HLA-G levels correlate with tumor progression, metastasis, and poor patient survival [13].
HLA-G interacts with inhibitory receptors ILT2, ILT4, and KIR2DL4 on immune cells, suppressing NK and T-cell cytotoxic responses [14]. Both membranebound and soluble isoforms (HLA-G1–G7) contribute to systemic immune suppression [15]. Because HLA-G expression provides tumors with a survival advantage, it represents a stable and functionally critical immunotherapeutic target [16].
Rationale for Targeting HLA-G
Unlike many tumor-associated antigens that are differentiation markers, HLA-G directly mediates immune escape [14]. Blocking or eliminating HLA-Gexpressing tumor cells may simultaneously remove a suppressive signal and restore endogenous immune responses [17].
Studies have demonstrated that high HLA-G expression is associated with resistance to immune checkpoint inhibitors [18]. Thus, targeting HLA-G could complement existing immunotherapies.
Additionally, HLA-G expression is relatively restricted in normal adult tissues, reducing the risk of severe systemic toxicity [11,12]. The presence of multiple isoforms broadens targeting potential and reduces the likelihood of antigen escape variants [15].
Design of Switch-Based Anti-HLA-G CAR-NK Cells
CAR Architecture
The engineered CAR construct consists of an extracellular antigen-binding domain recognizing HLA-G1–G7 isoforms, a hinge and transmembrane region, and intracellular signaling domains such as CD28 or 4-1BB fused to CD3ζ [19]. The addition of costimulatory domains enhances NK cell activation, persistence, and cytotoxicity [20].
An inducible caspase-9 (iCasp9) suicide gene is incorporated to enable pharmacological elimination of CAR-NK cells in case of adverse events [7]. This safety mechanism has been clinically validated in adoptive cell therapy settings [7].
Switch-Based System
The switch-based CAR platform employs a universal receptor that recognizes a tagged adapter molecule rather than directly binding HLA-G. The adapter consists of an HLA-G-specific antibody fragment fused to a peptide tag recognized by the CAR [8].
Advantages include:
Overcoming Solid Tumor Barriers
Antigen Heterogeneity
Tumor antigen heterogeneity remains a primary cause of therapeutic resistance [4]. Because HLA-G expression is functionally linked to immune evasion, tumors are less likely to completely lose expression without compromising survival advantage [16].
Immunosuppressive Tumor Microenvironment
The TME contains regulatory T cells, myeloid-derived suppressor cells, and inhibitory cytokines such as TGF-β and IL-10 [3]. HLA-G contributes directly to this suppressive network by inhibiting NK cell activation [14].
Elimination of HLA-G-expressing tumor cells may:
NK Cell Advantages
NK cells recognize stress-induced ligands independently of MHC restriction [9]. Their shorter lifespan may reduce long-term toxicity risks compared to CAR-T cells [10]. Additionally, NK cells produce lower levels of pro-inflammatory cytokines associated with severe cytokine release syndrome [9].
Preclinical Evaluation Strategy
In Vitro Studies
In Vivo Models
Xenograft mouse models expressing HLA-G will be used to evaluate:
CAR-NK therapy offers advantages in scalability and safety [10]. Off-the-shelf NK platforms derived from cord blood or induced pluripotent stem cells may enable broader clinical application [9].
HLA-G targeting may be particularly relevant for:
Combination strategies with checkpoint inhibitors may further enhance therapeutic efficacy [18].
Conclusion
HLA-G represents a compelling immunotherapeutic target in solid tumors due to its broad expression and central role in immune suppression [5,14]. A switchbased anti-HLA-G CAR-NK platform incorporating inducible caspase-9 offers enhanced safety, controllability, and adaptability [7,8].
This strategy addresses key barriers limiting CAR therapy in solid malignancies, including antigen heterogeneity and the immunosuppressive tumor microenvironment [3,4]. Continued preclinical validation and clinical translation may establish HLA-G–targeted CAR-NK therapy as a nextgeneration approach for solid cancer treatment.
References